| 摘要 |
PURPOSE:To perform recording, reproduction, and erasure freely by using a record carrier obtained by providing reproduction-only memory on one surface of an optical disk and reversible memory on the other, and performing tracking while reproducing and referring to information in the reproduction-only memory. CONSTITUTION:Light from a laser 1 is divided by a grating 2 into three beams, which are reflected by a polarizing prism 5 after passing through a collimator lens 3 and a half-wavelength plate 4, and then focused on the aluminum film 9a of a recording plate 9 through a quarter-wavelength plate 6, a tracking mirror 7, and an objective lens 8. The reflected beam travels backward to reach a four-split photodetector 15 through a condenser lens 14. The laser beam transmitted through the polarizing prism 5, on the other hand, is focused on the MnBi thin film of the recording plate 9 through a Faraday rotating element 10, a tracking mirror 12, and an objective lens 13. The reflected beam travels backward to reach the photodetector 15 through the condenser lens 14. Therefore, recording, reproduction, and erasure are performed freely. |
